Crosslinked starches

A crosslinked starch was described as a fluid loss additive for drilling fluids [632,1626]. The additive resists degradation and functions satisfactorily after exposure to temperatures of 250° F for periods of up to 32 hours. To obtain crosslinked starch, a crosslinking agent is reacted with granular starch in an aqueous slurry. The crosslinking reaction is controlled by a Brabender... 

Viscometer test. Typical crosslinked starches are obtained when the initial rise of the viscosity of the product is between 104° and 144° C, and the viscosity of the product does not rise above 200 Brabender units at temperatures less dian 130° C. The crosslinked starch slurry is then drum-dried and milled to obtain a dry product. The effectiveness of the product is checked by the API Fluid Loss Test after static aging of sample drilling fluids containing the starch at elevated temperatures. The milled dry product can then be incorporated into the oil well drilling fluid of the drill site. 

When a starch is treated with bi- or multi-functional reagents, crosslinking occurs. The reaction takes place in a slurry. With increasing degrees of crosslinking, starch... 

The effect of acid and dissolved solids is discussed under ingredient interaction. Since the combined effects of heat, acid and shear are additive, delay in the addition of acid until after cooking will allow a less-crosslinked starch to suffice. Similarly, delay in the addition of sugar will allow a more-crosslinked starch to be adequately... 

The approaches that were offered are illustrated in the patent literature of the time. Chiu et al.121 claim that starch heated after being adjusted to an alkaline pH value and then dried would behave as though it was crosslinked. In a patent awarded in 1999, Mahr and Trueck122 claim the use of amylose-containing starches complexed with lipid to enhance tolerance to thermal processing. Kettlitz and Coppin123 treated starch with activated chlorine to create a native product that was temperature-tolerant like a conventionally crosslinked starch. 

The texture of fruit pulp or tomato paste can be achieved in nonstandardized products, such as pizza sauces, through the introduction of texturizer starches. These are typically highly crosslinked starches that are subsequently drum dried. 

Englyst et al.248 classified starch into three types RSI, RS2 and RS3. RSI is a starch protected from digestion in the small intestine by a food matrix, such as the intact endosperm of a wheat kernel. RS2 is simply unswollen granular starch. RS3 is starch that was gelatinized, but then retrograded to become enzyme-resistant. Chemically modified (e.g. crosslinked) starch (RS4) has been added to the list.242 The four forms of resistant starch and their measurement are described by Nugent246 and Sajilata et al.249... 

Because consumers have become more mindful of what is in their diet, and because in the European Economic Community chemically-modified starches must be labeled as such, there has developed an interest in starches that have only been heated to achieve the process tolerance and short texture of a lightly-crosslinked starch. Such developments in modifying the properties of starch without chemical derivatization are discussed in two chapters. 

For mechanical stability against hydration and swelling, starch is chemically crosslinked (by adipic acid-acetic anhydride, phosphate, etc.) below Tgz, so that the physical integrity of the granules is not impaired by gelatinization. Weakly crosslinked starches (DS < 0.1) are acid-stable and thus find occasional application in recipes containing vinegar. The many industrial functions of crosslinked starch include use as an adhesive. 

The crosslinking of starch at the droplet interface in inverse miniemulsion leads to the formation of hydrogels. The formulation process for the preparation of crosslinked starch capsules in inverse miniemulsion is schematically shown in Fig. 10. The influence of different parameters such as the amount of starch, surfactant P(E/B-fe-EO), and crosslinker (2,4-toluene diisocyanate, TDI) on the capsule size and stability of the system were studied. The obtained capsules were in a size range of 320-920 nm. Higher amounts of starch and surfactant result in a smaller capsule size. The TEM images of crosslinked starch capsules prepared with different amount of crosslinker (TDI) are presented in Fig. 11. The nanocapsules can be employed as nanocontainers for the encapsulation of dsDNA molecules with different lengths [114] and for the encapsulation of magnetite nanoparticles. 

Fig. 10 Preparation of crosslinked starch capsules in an inverse miniemulsion...

Baier G, Musyanovych A, Dass M, Theisinger S, Landfester K (2010) Crosslinked starch capsules prepared in inverse miniemulsion as nanoreactors for dsDNA and polymerase chain reaction. Biomacromolecules 11 960-968... 

On the other hand, superabsorbent polymers having anionic groups that were made from low crosslinked starch or synthetic polymers were found to have high... 

WI Starch Xanthate. Research by Wing and others (22, 27-29) has shown that water-soluble (WS) starch xanthates, in combination with cationic polymers to form polyelectrolyte complexes, can effectively remove heavy metals from waste water. To eliminate the expensive cationic polymer and give a more economical method of heavy metal removal, further research by Wing and others (12,30-33) showed that xanthation of a highly crosslinked starch yields a water-insoluble (WI) product that is effective in removing heavy metals from waste water without the need for a cationic polymer. In more recent work, Tare and Chaudhari (34) evaluated the effectiveness of the starch xanthate (WS and WI) process for removal of hexavalent chromium from synthetic waste waters. 

Additional information on starch ethers has been reported by Pringsheim,1264 Hjermstad1265 as well as Banks and coworkers,1266 and Mishler1267 [only (hydrox-yethyl)starch], Omae and coworkers1268 [only (hydroxypropyl)starch adhesives], Hjermstad,1269 Mehltretter,1270 Moser1271 [(hydroxyethyl)starch], Tuschhoff1272 [(hydroxypropyl)starch], and Wurzburg1273 (crosslinked starches). 

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